Hiya
If you want to go and stay in Fethiye for couple of days I would recomend the Bus company PAMUKKALE.
They go everyday from
Marmaris to Fethiye at 10:00 in the morning.
They go as well from Fethiye to Marmaris everyday at 14:00 in the afternoon.
The price is 16 lira each way. The busses is very clean and with aircon.
You can book the ticket on the corner of Tansas supermarket in Marmaris.
If you order the tickets day before you are sure to have seats on the bus.
There is also service bus to the bus station from the corner of Tansas in Marmaris.
I use the Pamukkale bus company for the last 7 years. I normally go with the company from the airport to Marmaris.
Becurse I use regular flights to Izmir wich is for me better than the charterflighs...
If you only want go for day trip to Fethiye I can recomend to go direct to the bus station.
It is small busses and take around 3 hours each way. They go from the morning early untill late in the evening.
Every half an hour they go.
If you need any help about bus connection im ready to help you...
Take care
Cu Karsten